The present invention relates to a sound producing apparatus for a vehicle, and more specifically relates to a sound producing apparatus which can be properly installed to a low-noise vehicle, such as an electric vehicle or hybrid vehicle, to notify an approach of the vehicle outside the vehicle.
This kind of low-noise vehicle produces a lower traveling noise than a conventional vehicle does, so there is a concern that pedestrians would not notice the vehicle approaching. Accordingly, it has been proposed that the vehicle produces a dummy traveling sound so that pedestrians or bicycle's riders can notice the vehicle approaching.
Japanese Patent Laid-Open Publication No. 2009-40318 discloses a technology of producing dummy sounds of a tire noise and an engine idling sound. Further, in a technology disclosed in Japanese Patent Laid-Open Publication No. 2008-168676, dummy sounds having a high frequency are produced for a close notification area where the distance from the approaching vehicle is relatively short, while dummy sounds having a low frequency are produced for a far notification area where the distance from the approaching vehicle is relatively long. In general, since the low-frequency sounds tend to be easily attenuated compared to the high-frequency sounds, it can be restrained that the dummy sounds are transmitted far away or widely by producing the dummy sounds of the high-frequency sounds with cutting the low-frequency sounds.
However, the dummy sounds are no more than noises for the surroundings of the vehicle, so that an advantage of superior silence of the low-noise vehicle may be deteriorated. Further, since the dummy sounds having the high frequency, which is generated from the dummy sounds, such as the tire noise or the engine idling sound, for imaging the vehicle by cutting the low-frequency sounds as described above, do not contain the low-frequency components very much, there is a concern that even if the pedestrians or the bicycle riders hear the dummy sounds, they would not properly recognize the dummy sounds, such as the tire noise or the engine idling sound. Accordingly, it would be difficult that the vehicle's approach can be recognized properly.